The present invention relates to an aircraft comprising a foldable aerodynamic structure, an articulation mechanism for said structure, and to a method of folding an aerodynamic structure.
There is a trend towards increasingly large passenger aircraft with higher performance efficiency (for example fuel burn reduction), for which it is desirable to have correspondingly large wing spans. However, the maximum aircraft span is effectively limited by airport operating rules which govern various clearances required when maneuvering around the airport (such as the span and/or ground clearance required for gate entry and safe taxiway usage). Large aircraft may also give rise to other problems as a result of their size. For example, the entrance/exit of existing infrastructure such as aircraft hangers, may be too small to allow passage of the aircraft, and may need to be modified.
In some known aircraft designs (typically military aircraft) each of the aircraft's wings comprises an outer region which may be folded about a generally chordwise hinge line, between a flight configuration and a ground configuration. Such arrangements may enable the aircraft to occupy a relatively small space when on the ground, but to still have a relatively large wing span for flight. The movement of the outer region about the hinge is typically effected by an actuator. In some designs, this actuator may be locked, or have a dedicated lock actuator(s) which effects a lock in order to hold the outer region in place. However, such a design requires the lock to be safe-life (i.e. a component that cannot fail). Some alternative designs comprise multiple locks to lock the outer region in place in the flight configuration. This has the advantage that there are multiple load transfer paths between the outer and inner regions, such that each lock can be fail-safe (i.e. failure of one or more locks would not be catastrophic as there is redundancy provided by the other locks). However, a design that uses a dedicated lock actuator(s) to lock/unlock the locks is relatively complex (both in terms of the number and weight of actuators, and the control/sensor arrangements needed to coordinate the folding of the wing).
The present invention seeks to mitigate at least some of the above-mentioned problems.